Favartia (Pygmaepterys) circinata, Houart & Héros, 2012

Houart, Roland & Héros, Virginie, 2012, New species of Muricidae (Gastropoda) and additional or noteworthy records from the western Pacific, Zoosystema 34 (1), pp. 21-37 : 24-26

Favartia (Pygmaepterys) circinata n. sp. ( Fig. 1I, J, M)

TYPE MATERIAL. — Holotype (lv) NMMBM 005342 .

MATERIAL EXAMINED. — Only known from the holotype.

TYPE LOCALITY. — SE coast ofTaiwan, 22°19’N, 121°29’E, 258 m [NO Ocean Researcher 1, TAIWAN 2002: stn DW149, Chan, Cosel & Richer-IRD coll., 20/ V /2002].

DISTRIBUTION. — Known only from SE Taiwan at the type locality.

ETYMOLOGY. — From Latin “circinata”: rounded, convex, because of the broadly-ovate last teleoconch whorl.

DESCRIPTION

Shell large for the subgenus, height 11.6 mm at maturity, height/width ratio 1.7. Biconical, broadly-ovate, lightly built, weakly squamous. Subsutural ramp narrow, weakly sloping, weakly concave. Protoconch and 1st teleoconch whorl blackish brown, gradually lighter coloured, from greyish brown on 2nd whorl to light tan on last teleoconch whorl. Outer apertural edge finely surrounded with dark brown line as well as base of axial varices, remnants of previous positions of the aperture. Brown line not extended on siphonal canal. Aperture white within.

Spire high with 1.5 protoconch whorls ( Fig. 1M) and five broadly convex, weakly shouldered teleoconch whorls. Suture of teleoconch whorls impressed. Protoconch small, whorls rounded. Diameter 500 µm. Terminal lip shallow, delicate, weakly curved.

Axial sculpture of teleoconch whorls consisting of low, weak, webbed varices, each with a weak shoulder spine. Other axial sculpture of numerous growth lamellae. Spiral sculpture of low, narrow, squamous primary cords and numerous squamous threads. First to 3rd teleoconch whorls with visible SP, P1 and P2, 4th whorl with SP, P1-P3, last whorl with SP, P1-P5, s5, P6, ADP, MP, ABP and numerous squamous threads on and between spiral cords. Spiral cords extending on varices, forming small, broad, open spinelets joined by squamous webbing, more obvious on high, narrow apertural varix. P2-P5 strongest, P1 weakly narrower and lower, P6 small, narrow, ADP and ABP low, narrow, MP higher and broader, same strength as P1.

Aperture moderately large, ovate. Columellar lip narrow with two small knobs abapically. Rim partially weakly erect, adherent at adapical extremity. Anal notch deep, broad. Outer lip weakly erect, smooth, with five strong, broad denticles within: IP, D1-D2 fused, D3, D4, D5. D1-D2 denticle

largest. Siphonal canal short, broad, straight, open.

Operculum and radula unknown.

REMARKS

This species is unique in Pygmaepterys and differs in many ways from all the other known species by its shell morphology and colour. The secondary spiral structure is apparently absent between primary cords P1-P5; however, examination of new material will probably show that some of the threads are in fact secondary cords of the same magnitude as some of the threads.